The present invention relates to a magnetoresistive effect head and a method of manufacturing the same and, more particularly, to a magnetoresistive effect head employed for magnetic recorders and a method for manufacturing the same.
With a recent trend for size reduction and capacity increase of magnetic recorders, the magnetic recording techniques have a tendency of rapidly increasing integration density. Magnetic transducers utilizing magnetoresistance (MR) (hereinafter referred to as MR heads) can obtain a large reproduction output, and is one of the most important techniques for propelling the density increase of the magnetic recording. The MR head is dealt with in "A Magnetoresistive Readout Transducer", IEEE Trans. on Magn., MAG7 (1970) 150.
In the MR head, it is necessary to apply a domain control uni-directional magnetic field (i.e., vertical bias field) to a magnetoresistive (MR) effect film (mainly Ni--Fe film) as a region susceptible to medium magnetic field in order to prevent Barkhausen noise. U.S. Pat. No. 4,103,315 discloses a method of applying a vertical bias field across a magnetism-susceptible region of an Ni--Fe layer (film) serving as a magnetoresistive effect layer. In this technique, an antiferromagnetic layer such as an Fe--Ni layer is laminated on end portions of the magnetism-susceptible region to provide, as the vertical bias field, a uni-directional magnetic field provided by exchange coupling at the interface of the Ni--Fe layer and antiferromagnetic layer.
In the disclosed structure, the Ni--Fe layer is formed continuously to cover, as well as the magnetism-susceptible region, the domain control uni-directional magnetic field generating regions with the antiferromagnetic layer formed therein. Since the Ni--Fe layer in the magnetism-susceptible region is continuous to the Ni--Fe layer in the regions which are magnetized by the antiferromagnetic layer, with the vertical bias magnetic field applied to the magnetism-susceptible region and with the antiferromagnetic layer formed, the magnetization of the ends of the magnetism-susceptible region are fixed by the exchange coupling to result in reduction of the sensitivity to the medium magnetic field. In addition, the Ni--Fe layer and horizontal bias soft magnetic layer (SAL layer) located outside the magnetism-susceptible region are adversely affected by magnetic fluxes from tracks other than the read track to result in noise generation.
Japanese Patent Laid-Open Publication No. Heisei 3-125311 discloses a vertical bias application method for overcoming the above drawbacks. In the disclosed method, an Ni--Fe layer is formed in only a magnetism-susceptible region, and a soft magnetic layer is formed on opposite end portions of the Ni--Fe layer for magnetization to generate a uni-directional magnetic field, which is used for the vertical bias application to the magnetism-susceptible region.
However, in the Japanese Patent Laid-Open Publication No. Heisei 3-125311 structure noted above the magnetism-susceptible region which is a central region is joined in a very slant surface having a very small dimension to the permanent magnet layer formed at its opposite ends and also an electrode layer laminated on the permanent magnet layer, and the electrical connection in this juncture is insufficient, resulting an increase in resistance of the MR head.
In a process of patterning the central region as the magnetism-susceptible region and forming the vertical bias layer at the opposite ends of the central region, as shown in FIGS. 1(a), 1(b), 2(c) and 2(d), a photo-resist stencil pattern is formed (FIG. 1(a)), a central region is then patterned by slant ion milling (FIG. 1(b)), then the vertical bias layer is formed by sputtering (FIG. 2(c), and then lift-off is made (FIG. 2(d)).
In this case, the magnetoresistive effect layer (MR layer) in the central region is usually hidden by a peak layer of the stencil mask, and the junction of the vertical bias layer and electrode layer that are formed as a result of round-about sputtering on the inner side of the stencil mask is found in difficult locality compared to the SAL layer or magnetic separation layer. The magnetoresistance layer is predominately low in resistance compared to the SAL layer or magnetic separation layer, and the difficulty of directly uniting the vertical bias layer or electrode layer to the magnetoresistance layer results in MR head resistance increase.